You might be asking "you can already pour honey, why do I need to make it into a syrup?". Well, if you try to add plain honey to a cocktail, you'll be left with a thick gooey mess that wont mix in, no matter how hard you try. By using honey syrup it will not only mix better but pour more easily too.
Using a clover or orange blossom honey is the most standard, but there are a ton of other honeys out there. Clover is likely your best bet, it's what is most commonly used in cocktails
There's a lot of places you can use honey syrup. You can try using it in an Old Fashioned in place of the simple syrup to add more flavor. Or you can use it in a gin sour to make one of my favorite cocktails, the Bee's Knees.